<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        header {
            color: red;
        }
    </style>
    <!--[if IE 8]>
    <script>
        alert('哈哈');
        document.createElement('header');
    </script>
    <![endif]-->
</head>
<body>

<header>
    这是一段文字
</header>
</body>
</html>